In order to be able to make a typical optical fiber communication system, it is necessary to be able to abuttingly join two optical fibers such that optical signals can pass from one fiber to the other with, desirably, only small loss. A well known technique for so joining two lengths of optical fiber is fusion splicing. See, for instance, C. M. Miller, "Optical Fiber Splices and Connectors", M. Dekker, Inc., 1986 especially pp. 282-293.
It is not only highly desirable that such fiber splices not introduce significant loss into the optical transmission path, but also that the splices have high mechanical strength. These requirements are particularly severe for, e.g., submarine optical fiber communication systems. Exemplarily, some systems require that splices pass a 200 ksi (13.8.times.10.sup.8 N/m.sup.2) tensile test, and some undersea systems require a 300 ksi (20.7.times.10.sup.8 N/m.sup.2) proof test.
As is well known, optical fiber conventionally comprises a polymer coating. This coating has to be removed from the relevant end portions of the fibers that are to be joined by fusion splicing. This is conventionally accomplished by dipping in hot (e.g., 180.degree.-200.degree. C.) concentrated sulfuric acid, whereby the coating is etched away. See, for instance, C. M. Miller, op. cit., page 292. Subsequent to fusion splicing the bare fiber portion typically is re-coated. By "etching" of the polymer coating we mean a chemical removal process that can result in a relatively sharp boundary of the remaining polymer, and does not damage the fiber. This is to be contrasted with a removal process, (e.g., one involving a swelling process) which does not result in a sharp boundary.
It has been observed that typically only a relatively small fraction (frequently &lt;50%) of prior art fusion splices can pass the 300 ksi strength test, frequently requiring re-splicing. This is obviously costly and thus undesirable. It will be understood that associated with a batch of fusion spliced optical fibers is a strength distribution, with a certain percentage of the fibers passing at a given proof test level.
In view of the importance of increasing the fraction of fusion splices that passes an appropriate strength test, a method of splicing optical fiber that can yield splices of improved strength would be desirable. This application discloses such a method.